This invention relates to a power disconnect assembly for a plug-in electric heating element.
Ranges and cooktops have for years utilized heating elements comprising a metal sheathed electric resistant heater which is wound to flat, spiraled formation with terminal portions connected to a source of electrical power. These heating elements are often plug-in type elements such that they can be manually plugged into a terminal block and unplugged from the terminal block for cleaning purposes or replacement of defective heating elements. Such a plug-in heating element arrangement is disclosed in U.S. Pat. No. 4,013,870.
It has also been known for many years that considerable electrical energy is wasted by reason of the fact that the user of ranges and cooktops often does not immediately turn the control switch to the "off" position after removal of a cooking utensil from the heating element. A number of prior art patents disclose means to detect either the presence or absence of a cooking vessel on a heating element and provide an arrangement for terminating electrical power to the heating element in the event the cooking vessel is absent from the heating element. One such arrangement is disclosed in U.S. Pat. No. 4,214,150. In addition, induction heating cooking units have also utilized cooking vessel detection arrangements again to terminate electrical power to the induction heating unit when a cooking vessel is not present on top of the unit. See, for example, U.S. Pat. No. 3,796,850. Another automatic power termination arrangement is disclosed in U.S. Pat. No. 4,164,644 wherein a portable electric heating unit utilizes a power disconnect assembly.
One of the problems that the prior art has not provided for is an arrangement whereby electric power to the terminal block is prevented in the event the plug-in heating element is removed from the terminal block and the control switch for the heating element is "on". Usually, the plug-in heating element is removed so the user can clean around the area of the heating element and terminal block. It is, therefore, desirable to have no electric power to the terminal block to eliminate any possible electric shock hazard. It is particularly useful to have a power disconnect assembly wherein a solid state control device is utilized to adjust or regulate the power available to the electrical heating element to control the heat output of the unit. Solid state control devices may fail in a short circuit condition and thus make available at the terminal block electrical power in the event the control is in an "on" position and the plug-in heating element has been removed.
By this invention, there is provided an automatic means for disconnecting the electrical power to the terminal block when a plug-in electric heating element is unplugged for the terminal block and also the means disconnects power to the terminal block in the event a cooking vessel is absent from the heating element surface.